1. Field of the Invention
The present invention relates to an apparatus and a method to encode information based on an ECC interleave structure.
2. Description of the Related Art
In magnetic recording, various sources of noise can corrupt accurate information (for example, thermal noise, interference, and media noise arising from sources such as jitter, DC erase noise, and pulse width/height modulation). Media noise is a dominant source of noise in many current recording systems. The media noise is usually treated as highly correlated non-stationary noise added to a read-back signal.
RLL Coding schemes use (d, k) constraints, which limit a minimum and a maximum run lengths of zeros, respectively, or alternatively, the schemes control high and low frequency contents of user data. Conventional high-rate RLL (0, k) codes are highly complex for circuit implementation and relatively xe2x80x9cblindxe2x80x9d in terms of error detection during a demodulation process. The d, k constraints include properties of the conventional codes exploitable for error control purposes. However, this specialized type of error is only a small subset of the total number of possible errors.
A construction of an encoder, which encodes arbitrary binary sequences into sequences, is needed that obeys a specific run-length-limited (RLL) constraint. It is important that the encoder encodes data at a high rate, that the decoder does not propagate channel errors, and that a complexity of encoding and decoding be low.
White noise is added to every symbol entering a channel in a magnetic recording medium. Media Noise, like white noise, is random. Unlike the white noise, the media noise is not added to every symbol. The denser a signal is written onto the magnetic recording medium, the more frequent media noise occurs. Thus, a recording density controls a ratio of media noise to white noise. For instance, a ratio of 50:50 may be one example.
In general, in magnetic recording systems, it is desirable that certain conditions are met where typical channel errors do not corrupt many blocks of a codeword in a same interleave, and that a length of typical channel errors is short. Also, it is desirable that short channel errors do not propagate into long decoder errors, and that a number of non-zero values over the codeword is large. If these conditions were not satisfied, then the magnetic recording medium would require a more powerful error correcting code (ECC), which increases hardware complexity of a magnetic recording system. Regarding the condition where the number of non-zero values over a codeword is large, the non-zero values over a codeword is large, the non-zero values are important because the non-zero values provide useful information to recover a system clock.
With respect to the condition where the length of typical channel errors need to be short, a long typical channel error may occur when for some pair of integers, k and M, where:
(x(k+1), x(k+2), . . . , x(k+M) )=x*(1 0 1 0 1 0 . . . ),
or
(x(k+2*1),x(k+2*2), . . . , x(k+2M))=x*(1 1 1 1 1 . . . ),
where x* xcex5{0, 1}
The apparatus and method according to an embodiment of the present invention, provide a system where the channel errors do not corrupt many blocks in the same interleave, where the length of the typical channel errors are short, and where the short channel errors do not propagate into long decoder errors.
Various objects and advantages of the invention will be set forth in part in the description that follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
In order to achieve the above and other objects, a system to modulate coding based on an ECC interleave structure, includes: a first encoder encoding an input stream of bits including input blocks sorted into interleaves; and a second encoder encoding a subset of the input blocks to produce output blocks, wherein the first encoder permutates a remainder of the input blocks and the output blocks to produce a codeword.
In order to achieve the above and other objects, a system to modulate coding based on an ECC interleave structure, includes: a first encoder encoding an input stream of bits, sorting the input bits into interleaves of input blocks, and selecting at least one subset of the input blocks, wherein each input block includes a predetermined input block size; a second encoder encoding the at least one subset of the input blocks to output blocks, wherein the first encoder permutates a remainder of the input blocks and the output blocks to prevent channel errors from being greater than a correction capability of the interleave; and a decoder inverse decoding the output blocks to restore the input blocks.
In order to achieve the above and other objects, a method to modulate coding based on an ECC interleave structure, includes: encoding an input stream of bits with a first encoder; sorting the input bits into interleaves of input blocks, each input block including a predetermined input block size; selecting at least one subset of the input blocks; encoding with a second encoder the at least one subset of the input blocks to output blocks; permutating a remainder of the input blocks and the output blocks to prevent channel errors from being greater than a correction capability of the interleave; and inverse decoding the output blocks to restore the input blocks.
In order to achieve the above and other objects, a method to modulate coding based on an ECC interleave structure, includes: selecting an n/m rate of a first encoder; receiving an input signal including input bits, b(i)""s, wherein i=1, 2, . . . n; selecting an input block size, S, for the input bits, b(i)""s; interleaving the input bits, b(i)""s, into blocks, (B1xe2x88x92Bk), each block including the input block size, S, wherein k=n/S; selecting at least one subset, (Bi1, Bi2, . . . , Biq), from the blocks, wherein q less than k; mapping the at least one subset, (Bi1, Bi2, . . . , Biq) to an output vector, f=(f1, f2, . . . , fp), of a second encoder within the first encoder, wherein p is a number of output bits, f, from the second encoder; and permutating ((f1, f2, . . . , fp), Bj1, Bj2, Bj(kxe2x88x92q)) to prevent channel errors from being greater than a correction capability in the interleave, wherein (Bj1, Bj2, . . . Bj(kxe2x88x92q))=(B1xe2x88x92Bk)xe2x88x92(Bi1, Bi2, . . . , Biq), are the blocks remaining after the at least one subset, (Bi1, Bi2, . . . , Biq), is selected and the permutating is a permutation, P, operating on the bits of vector ((f1, f2, . . . , fp), Bj1, Bj2, Bj(kxe2x88x92q)).
In order to achieve the above and other objects, a computer readable medium storing a program for controlling at least one computer to perform a method includes: encoding an input stream of bits with a first encoder; sorting the input bits into interleaves of input blocks, each input block including a predetermined input block size; selecting at least one subset of the input blocks; encoding with a second encoder the at least one subset of the input blocks to output blocks; permutating a remainder of the input blocks and the output blocks to prevent channel errors from being greater than a correction capability of the interleave; and inverse decoding the output blocks to restore the input blocks.
These together with other aspects and advantages which will be subsequently apparent, reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout.